1. Field of the Invention
This invention relates to footwear.
2. Description of the Prior Art
It is known in the prior art to form cushioned insoles for footwear from low density polyurethane having, for example, a specific gravity in the range of between approximately 0.35 and 0.45. The lower the specific gravity the greater is the cushioning effect of the insole. A limiting factor in the use of such low density polyurethane is that in certain footwear forming processes, such as the flat lasting process, an insole formed of low density polyurethane is not strong enough to retain the stitching between the insole and the upper when the stitches are tightened.
On the other hand, insoles formed of higher density polyurethane are not so limited because they are strong enough to retain the stitching between the insole and the upper as the stitches are tightened. However, these higher density polyurethane insoles provide less cushioning than do the lower density polyurethane insoles.
One prior art solution is to locate the low density polyurethane insole below a firmer cloth cover which is stitched to the upper. The firmer cloth cover, unlike the low density polyurethane, is strong enough to retain the force of the stitching when the stitches are tightened. However, because the wearer's foot is on the harder cloth cover, the cushioning effect of the underlying low density polyurethane insole is substantially diminished.